Circuit breaker



Dec. 29, 1970 R. c. INGWE'RSEN CIRCUIT BREAKER 2 Sheets-Sheet 1 FiledMarch l2. 1969 INVENTOR ATTORNEYS United States Patent Omce 3,551,867Patented Dec. 29, 1970 3,551,867 CIRCUIT BREAKER Richard C. Ingwersen,Treasure Island, Fla., assignor to Allied Control Company, Inc., NewYork, N.Y. Filed Mar. 12, 1969, Ser. No. 806,664 Int. Cl. Htllh 71/16U.S. Cl. 337-63 7 Claims ABSTRACT F THE DISCLOSURE A trip-free circuitbreaker of the push-pull type having a rocker lever carried on thepush-pull actuator, the rocker lever having a fulcrum point at one endand a contact at the other end, and a mechanical latch carried on therocker lever and having unitary pivotal movement therewith forsupporting the rocker lever in circuit closing position.

BACKGROUND OF THE INVENTION embodied a relatively large number ofcomponents parts including molded parts with metal inserts. Inproduction such devices have 'been diicult to calibrate and have had atendency to lose their calibrations under service conditions, especiallyunder conditions involving vibration and repetitive manual actuation.Surface wear in such prior circuit breakers has been the cause of mostof the problems experienced.

SUMMARY OF THE INVENTION According to the present invention, an allmetallic actuator has been provided with the elimination of all moldedparts with metallic inserts. By redesigning the functional structure ofthe circuit breaker, in the order of 35% fewer parts are employed overpreviously accepted commercial designs. The resulting simplicity makesthe circuit breaker easier to assemble and materially reducescalibration problems. At the same time a substantial reduction inmanufacturing cost is realized as the parts are fewer and simpler, thereis less scrap of plastic parts and nish requirements have beenminimized. Moreover, it has been possible to effect a substantial savingin initial tooling cost as Well as reducing the cost of toolmaintenance.

Obviously, the aforementioned improvements in cost savings would be ofno practical consequence without an accompanying high degree ofreliability. To that end all critical wear surfaces of the circuit'breaker are either work hardened, as in the case of the thermostaticbimetal, or heat treated as in the case of the beryllium coppercomponents. Also, the stored forces for effecting circuit breaking uponoverload are well balanced to avoid cocking and binding of the componentparts.

DRAWINGS In the illustrated forms of the invention, FIG. 1 is a sideelevational view of one form of the circuit breaker with the front halfof the case shown removed and the circuit closed,

FIG. 2 is a cross-sectional view taken on line II-II of FIG. 1,

FIG. 3 is a view similar to FIG. 2 taken on line III- III of FIG. 1,

FIG. 4 is a fragmentary plan view of the contact rocker member,

FIG. 5 is a fragmentary sectional view through the shoulder screw of theactuator elements,

FIG. 6 is a View similar to FIG. 1 showing the circuit open,

FIG. 7 is a fragmentary view similar to FIG. 1 showing the circuit aboutto be closed by manual operation,

FIG. 8 is an exploded view of the component parts shown in FIG 1, and

FIG. 9 is a fragmentary side elevational View of a modified form ofcontact.

DETAILED DESCRIPTION In the form of the invention shown in FIGS. 1through 8, the circuit breaker 10 comprises a molded case having a frontpart 12 and a back part 14 held together by four suitable fasteners 16.Terminals 18 and 20 are received in opposed slots provided in the parts12 and 14 in a Well known manner. A suitable panel attachment bushing 22is received in opposed semi-circular depressions in the parts 12 and 14in an equally well known manner. Attached to the terminal 18 by welding,or otherwise, is the thermal element 24. A lixed contact 26 is carriedon the terminal 20.

ACTUATOR MECHANISM The mechanism for manually opening and closing thecircuit breaker 10 through the exposed actuator button 28 of suitableinsulating material, comprises two separate, relatively movable linearmembers preferably stamped from a sheet of half hardened beryllium. Onesuch element is in the form of an actuator slide 30 having a hole 32 inits lower end to receive a pin 34 of insulating material to attach thebutton 28 to the slide 30. The upper end of the slide 30 is bent toprovide an anchor tab 36 for the extension spring 38. Between the endsof the slide 30, a laterally extending latch cam 40 is provided.

The other element of the actuator mechanism takes the form of anactuator bar 42 having a tapped hole 44 to receive the threaded end 46of the shoulder screw 48. An elongated hole 50 is provided in theactuator slide 30 in. which the cylindrical shank 51 of the screw 48 isdisposed, the head of the screw 48 holding the slide 30 and bar 42assembled to each other, yet permitting limited lost motion along theirlongitudinal axes defined by the amount of clearance of the shank 51 ofthe screw 48 in the elongated hole 50. Above the hole 44 and centered onthe bar 42 is a reamed hole 56 to receive a suitable shoulder rivet 57for pivotally supporting the contact rocker lever assembly.

To guide the slide 30 and bar 42 of the actuator mechanism forlongitudinal movement, the back part 14 of the case is provided with agenerally rectangular depression 58 which, with the surface 60 of thefront part 12 of the case, provides a four sided guide for the upper endof the bar 42. The lower end of the bar 42 is supported for longitudinalmovement between the projections 62 defined on the horizontal leg of theL-shaped guide 64. The vertical leg 65 of the guide 64 is shown attachedto an interior wall surface of the back part 14 of the case by drive pin65', or other suitable means.

Actuator slide is supported for longitudinal movement in the rectangularslot 66 provided in the insulating bushing 68 disposed within the panelattachment bushing 22 with a press t. As the button 28 and the tripindicator 70 are both located within the bushing 68 with a free guidingtit, the relatively snug llt between the lower end of the slide 30 andthe slots in the button 28 and trip indicator 70 results in the slide 30having a relatively long support bearing in the bushing 68 andovercoming any tendency to cock or bind.

In practice, there is relatively little lateral clearance bctween thediameter of the shank 51 of the shoulder screw 48 and the parallel sidesof the elongated hole 50 through which the screw 48 extends. As aresult, the upper end of the slide 30 is guided for longitudinalmovement relative to the actuator bar 42 upon the shank 51 of the screw48, When the limits of relative movement are reached, as defined by theends of the elongated hole 50, the slide 30 and bar 42 will have unitarymovement and the upper end of the slide 30 will be guided by the bar 42,the `bar 42, in turn, being guided in its movement by the depression 58and surface 60 and the projections 62 on the guide 64.

CONTACT ROCKER LEVER ASSEMBLY The movable contact 72, which is engagedand disengaged with the fixed Contact 26 to make and break the circuit,is carried upon a contact rocker lever assembly 75 pivotally supportedon the actuator bar 42 by the shoulder rivet 57. Preferably, the rockerlever comprises front and rear parts 76 and 78, one of which is themirror image of the other except for the size of the holes 74 to receivethe stepped down diameter of the shoulder rivet 57. Outturned ears 80and 82 are provided on the parts 76 and 78 to which is secured to thecontact blade 84 by rivets or drive pins 85. The movable Contact 72 iscarried on the `blade 84.

In practice, the parts 76 and 78 are stamped from quarter hard berylliumcopper sheet while the contact blade 84 is formed from half hardberyllium copper sheet. It will be seen from FIG. 4 that the centralportion 86 of the parts 76 and 78 are outwardly offset to provideclearance space 42 for the actuator bar 42, the clearance space beingsufficient to enable the assembly of the parts 76, 78 and 84 to pivotthrough a substantial arc on the bar 42 about the axis of the shoulderrivet 57. The depth of the offset of each central portion 86 isapproximately onehalf the thickness of the bar 42 whereby the rockerlever assembly, while freely pivotable on the bar 42, is lirmlysupported and guided by opposite sides of the bar 42 directly adjacentthe hole 56 in the bar 42 through which the shoulder rivet 57 extends.Each of the parts 76 and 78 have a spring tab portion 88 at one end anda ledge portion at the opposite end, which ledge portion of each of theparts 76 and 78 collectively form a two-ply ledge 90. The insulatingbushing 68 is provided with spring anchor tabs 94 and 96, the spring 38being attached to the tab 94 and the extension spring 98 being attachedto the tab 96.

THERMAL ELEMENT The thermal element 24 is formed in part from a strip 24of suitable thermostatic bimetal or trimetal material having aresistance to suit the desired ampere rating. In form, it is generallyU-shaped with one vbimetallic leg 100 welded or riveted to anonthermostatic L-shaped member having at its upper end a llange 104which is welded, or otherwise rigidly attached, to the terminal 18. Theother bimetal leg 106 of the strip 24 has, at its upper end, an offsetinturned flange 108 having its active portion substantially disposed onthe center line of the case delined by the parts 12 and 14. As the lowexpansion side 4 of the thermostatic strip 24' is disposed on theoutside of the legs 100 and 106, on overload the leg 106 will bedisplaced to the left, as viewed in FIGS. 1 and 6. An adjustment screw24, disposed in a threaded aperture on the part 14, bears against asurface of the nonthermal member 102 to shift the position of the flange108 relative to the two-ply ledge 90 of the contact rocker leverassembly 75.

MECHANICAL LATCH When the actuator bar 42 is in its closed circuitposition, which is its up position as seen in FIG. l, the bar 42 is heldagainst the tension of the extension spring 98 by the mechanical latch109 rigidly attached at one end to the rocker lever assembly adjacentthe two-ply ledge 90. Preferably, the mechanical latch 109 s formed froma sheet of half-hard beryllium copper. As stamped from the sheet, thelatch blank is perforated to receive the twoply ledge and is flanged torest on top of the parts 76 and 78. The upper perforated end of thelatch 109 is then welded in position on the ledge 90 and, thereafter,heat-treated along with the assembly 75. The vertical leg of the latch109 depends from the rocker lever assembly 75 to terminate in anangularly disposed portion 116 adapted to rest on one of the projections62 on the guide 64. The latch 109 is of sufficient width as to enablethe nose portion 116 while resting on the projection 62 to also extendlaterally therefrom a sufficient distance to be engaged by the latch cam40 on the actuator slide 30. With the circuit closed, the latch cam 40is disposed out of actuating contact with the nose portion 116. When thecam 40 is lowered by manual movement of the slide 30 engages thatportion of the nose portion 116 laterally disposed with reference to theprojection 62 and urges the nose portion 116 from its position ofsupport on the projection 62 whereupon the component parts collapse intothe position similar to that disclosed in FIG. 6 with the exception thatthe leg 106 of the thermal element will not be thermally displaced, asshown in FIG. 6, but will be disposed in the position shown in FIG. 7.

At the time the actuator slide 30V is lowered by manual force applied-to the button 28 to manually open the circuit breaker, as described inthe preceding paragraph, the lost motion connection between the slide 30and the bar 42 enables the latch cam 40 to move into engagement with thenose portion 116 of the latch portion 109 without movement beingimparted to the bar 42 upon which the rocker lever assembly 75 iscarried. As the assembly 75 is held against clockwise pivotal movementabout the axis of the shoulder rivet 57 by engagement of the twoplyledge 90 with the fulcrum abutment flange 108, the nose 116 will tend toresist movement along the face of the projection 62 upon which it restsand some deflection of the latch 109 must take place before the noseportion 116 can be displaced by the latch cam 40. Through thisarrangement the resiliency of the latch 109 resists manual movement ofthe slide 30 along. with the tension of the springs 38 and 98. Also, anytendency for the nose portion 116 of the latch 109 to be vibrated offits position of normal rest upon the projection 62 is avoided.

OPERATION In FIG. 6, the actuator bar 42 is shown in its down positionfollowing an overload. The thermal strip 24', having been overheated, isshown with the leg portion 10'6 moved to the left from the positionshown in FIG. 1. The actuator slide 30 is, likewise, in its downposition with the button 28 in its extreme projected position and thetrip indicator 70 is disposed to visually indicate that the circuitbreaker has been actuated and the circuit is open.

Upon cooling, the thermal strip 24' will return to the position in FIGS.1 and 7 to relocate the flange 108 inthe path of movement of the two-plyledge 9 0 of the contact rocker lever assembly 75. To restore thecircuit breaker to its closed circuit position of FIG. l, an upward pushis exerted on the button 28 to raise the actuator slide 30 into theposition shown in FIG. 1. As the shoulder screw 48 on the bar 42 isresting on the lower end of the elongated hole 50 in the slide 30 withthe circuit open, the bar 42 will move upwardly as a unit with the slide30.

As the bar 42 moves upwardly, the two-ply latch 90 will engage beneaththe flange 108 to swing the contact rocker lever assembly 75 into theposition shown in FIG. 1 with the movable contact 72 in stressedengagement with the fixed contact 26 to close the circuit.

To support the bar -42 in the position shown in FIG. l closing thecircuit, the latch 109 must be so located and shaped, as well ascalibrated by adjustment of the screw 24", so as to dispose the latchnose portion 116 on the projection 62 of the fixed guide 64. Thenecessary movement of the latch 109 is assured by the engagement of thetwo-ply ledge 90 with the underside of Ithe fulcrum ange 108 whichcauses the contact lever assembly 75 to be rocked counterclockwise as itis being simultaneously lifted on the bar 42. With this movement takingplace the latch cam 40 is disposed in its elevated position clearing thenose 116, as shown in FIG. 7. The continued forward movement of the bar42 will cause the nose portion 116 of the latch 109 to be snapped overthe edge of the projection `62 and upon the latch supporting surfacethereof into its final position of rest, as shown in FIG. 1.

With the component parts in the position shown in FIG. 1 the springs 38and 98 are fully tensioned. If the manual force holding the button 28fully elevated is then removed, only the latch 109 with its nose 116resting on the projection 62 is acting to prevent the tension of thesprings 38 and 98 from collapsing the circuit breaker components intothe open circuit position of FIG. 6.

It will be understood, with the component parts shown in FIG. 1, thatthe tension of the spring 38 on the slide 30 is being resisted by thecam 40 resting on the nose portion 116, the tension of the spring 38being insufficient to cause the cam 40 to displace the nose 116` fromits position of rest on the projection 62 with the circuit closed.

Upon the occurrence of the short or overload, the flange 108 will bemoved from its latching position above the two-ply ledge `90 and thetension of the spring 98 will rock the contact lever assembly 75 aboutthe axis of the shoulder rivet 57 to separate the contacts 26 and 72with snap action. As the latch 109 will have unitary movement with theassembly 75, the rocking action on the part of the assembly 75 willremove the latch nose 116 from the projection 62 and the component partswill collapse into the state shown in FIG. 6.

Preferably, the combined length of the latch 109 and its nose portion116 is such that some slight deflection of the thermal element 24 andthe resilient contact blade 84 carrying the movable contact 72 isrequired to raise the bar 42 sufliciently to allow the latch nose 116 toswing counterclockwise into its position of rest above the projection62. Thus, when the manual force on the button 28 is released, the latch109 is supporting the stress of the deflection of the thermal element 24and the contact blade 84 as well as the tension of the spring 98. Itwill be noted that all of these forces are acting in substantially thesame vertical plane.

It should be further noted that only with respect to the thermal element24 is there any provision for calibration. All the components whichreact against the thermal element 24, directly or indirectly, aresubstantially in balance and act only in the plane in which the bar 42and the active part of the flange 108 are disposed. In this regard thecontact lever assembly 75 comprises two similar parts disposed onopposite sides of the bar 42 and presenting a two-ply support definingthe ledge portion 90 to the flange 108. Likewise, the latch 109 is incomplete balance on the bar 42. By supporting the latch nose 116 on thatportion of the projection 62 disposed in the plane of the bar -42substantial balance is maintained with respect to the forces acting onthe latch 109 through the shoulder rivet 57.

As to the forces which are brought to acton the latch nose 116 throughthe latch cam 40, it will be observed that the cam 40 is injuxtaposition to the plane of the bar 42.

For the sake of clarity, the usual flexible conductor 120, extendingbetween the contact 72 and the thermal element 24, is shown broken awayexcept for its points of attachment with the contact blade 84 and thetab 122 on the leg 106.

MODIFICATION In FIG. 9 is shown a modification of the movable contactstructure in which the contact 124 is carried upon an L-shaped arm 126pivotally supported on the contact lever assembly on the pivot pin 128.A stop 130 limits rocking of the arm 126 counterclockwise about the axisof the pin 128 under the stress of the spring 98. Clockwise movement ofthe arm 126 will increase the tension on the spring 98 with the reactionbeing taken by the contacts 26 and 124.

I claim:

1. In a trip-free circuit breaker of the type described, the combinationwith an actuator, of a rocker lever pivotally supported on said actuatorintermediate the ends of said lever, one end of said lever constitutinga fulcrum point and the other end carrying a movable contact, a fixedbody portion in which said actuator is disposed for relative movement, afixed contact carried on said body portion, a thermostatic conductorincluding a fulcrum displaceable upon overload with which said fulcrumpoint normally engages to rock said lever about its pivot point uponmanual manipulation of said actuator in one direction to imparttranslatory motion to said lever, during said manipulation and followingengagement of said fulcrum point with said fulcrum said lever is causedto rock about said fulcrum point to move said movable contact intoengagement with said fixed contact to close the circuit in which saidthermostatic conductor is disposed, energy-storing means energized bysaid manipulation and tending to rock said lever in a direction toseparate said contacts to open the circuit said means being operativelyconnected between said body portion and said lever, a mechanical latchcarried on said lever and having a unitary pivotal movement therewithfor supporting said lever in circuit-closing position and resisting saidenergystoring means with said fulcrum point engaging said fulcrum andrestraining pivotal movement of said lever about its pivot in acircuit-opening direction, and means supporting said thermostaticconductor relative to said fulcrum point whereby the heat of an overloadwill displace said fulcrum from engagement with said fulcrum point toenable said lever to be rocked by said energy-storing means in adirection to open the circuit.

2. In a trip-free circuit breaker of the type described in claim 1having means on said actuator for operating said latch when saidactuator is moved in the opposite direction to enable the pivot of saidlever to move relative to said fulcrum to rock said lever in a directionto separate said contacts to open said circuit.

3. In a trip-free circuit breaker of the type described in claim 2wherein said actuator is manually manipulated in both directions to openand close the circuit.

4. In a trip-free circuit breaker of the type described in claim 1wherein said actuator is of the push-pull type having two linear partswith a lost motion connection between them, said lever being pivotallycarried on one of said parts and means on the other of said parts forengaging said latch to render the same inoperative when said actuator ismoved in a direction to open said circuit.

5. In a trip-free circuit breaker of the type described in claim 4wherein a cam is provided on said other part and disposed adjacent saidseat for displacing said latch from said seat upon movement of saidother part in a. circuit-opening direction.

7 8 6. In a trip-free circuit breaker of the type described ReferencesCited in claim 1 wherein a xed seat is provided for said latch, UNITEDSTATES PATENTS said latch having a portion for engaging said seat t0resist rocking movement of said lever about its pivot with 281619212/1957 Ingwersen 337-63 said fulcrum point engaging said fulcrum. 5BERNARD A. GILHEANY, Primary Examiner 7. In a trip-free circuit breakerof the type described D M MORGAN Assistant Examiner in claim 6 whereinsaid latch, when engaged on said seat, reacts against said lever at apoint between one end of U.S. C1. X.R. said lever and its pivotalconnection with said actuator. 337-66, 74

